Centre a wide character's glyph in its two cells

A Hangul or CJK glyph is one em across, less than two cells of a
monospace Latin font (1.2 em for DejaVu Sans Mono), and was drawn from
the left of its cells, so syllables stood apart unevenly. A cached
glyph now keeps its advance in pixels, and a wide character's glyph is
drawn centred in its two cells.

2 files changed, 3 insertions, 2 deletions

diff --git a/symbols/symbols.c b/symbols/symbols.c
index f00639a..2ee5d5e 100644
--- a/symbols/symbols.c
+++ b/symbols/symbols.c
@@ -237,7 +237,7 @@ const VegaBitmap *vega_glyph(VegaGlyphs *glyphs, uint32_t code) {
     if (pixels)
         vega_symbol_raster(glyphs->symbols, &symbol, glyphs->scale, place.left / glyphs->scale, place.top / glyphs->scale,
                            place.width, place.height, pixels, (size_t)place.width);
-    slot->bitmap = (VegaBitmap){place, pixels};
+    slot->bitmap = (VegaBitmap){place, pixels, (int)lroundf(symbol.advance * glyphs->scale)};
     return &slot->bitmap;
 }
 
diff --git a/symbols/symbols.h b/symbols/symbols.h
index 0af3412..32f48d0 100644
--- a/symbols/symbols.h
+++ b/symbols/symbols.h
@@ -62,7 +62,8 @@ void vega_symbol_raster(const VegaSymbols *, const VegaSymbol *, double scale, d
 
 /* Symbols drawn once at one scale and kept, for surfaces that compose them
  * on the CPU: each the first time it is asked for. */
-typedef struct { VegaPlace place; const unsigned char *pixels; } VegaBitmap; /* pixels: place.width per row */
+/* pixels: place.width per row; advance: how far the pen moves after it, in whole pixels */
+typedef struct { VegaPlace place; const unsigned char *pixels; int advance; } VegaBitmap;
 typedef struct VegaGlyphs VegaGlyphs;
 VegaGlyphs *vega_glyphs_open(const VegaSymbols *, float scale);
 /* The bitmap of code, or NULL when the file has no such symbol. */